Patent GB-1409469-A (GB)
Title: Power transmission and water craft using such transmission
IPC: B60K17/06
Filed: 1973-05-09
Abstract: 1409469 Reverse gear control TWIN DISC Inc 9 May 1973 [10 May 1972] 22007/73 Heading F2D [Also in Division G3] In a marine reverse gear having modulatable forward and reverse friction clutches the output speed of which is determined by the magnitude of hydraulic pressure applied through respective lines 100, 101, Fig. 6, to engage them, such pressure is controlled by a rotary selector valve 72, Figs. 1, 6, initial rotation of which, in either direction from neutral, pressurizes the selected clutch, whilst further rotation, in the same direction, causes the pressure level to increase in direct proportion to the extent of the rotation, by controlling the axial position of a pressure regulating spool 79. The rotary selector valve 72 receives supply pressure through a central axial passage 93 and passages 91, 92, 81, the communication of which last named, 81, with supply and exhaust mains 80, 82, is controlled by the - regulator spool 79 under rightward loading of springs 87, 88 and leftward by a light spring 83 and regulated pressure 81 supplied to its right end 84 through a passage (85, Fig. 2, not shown). Compression of the load springs 87, 88 is determined by the axial position of a non-rotary piston 77 which thus determines regulated pressure. The piston 77 is subject on its left face to pressure in a chamber 107 in permanent communication with supply 80 through a passage 67a and restrictor 67d, Fig. 4b, the chamber 107 exhausting to the right side of the piston 77 through a controllable exhaust port 72e in the stem 72a of the rotary selector valve 72 and controlled as follows. Surrounding the stem 72a and integral with the non-rotary load piston 77 is a sleeve 77b having a rightwardly tapering cut-out 77d, Fig. 4b, through which the port 72e exhausts. Initially, with the rotary selector valve 72 in neutral, the regulator load-piston 77 is at its extreme left and the port 72e exhausts through the cut-out 77d. Turning the selector valve 72 to pressurize the forward or reverse clutch passage 100, 101, and exhaust the opposite clutch through passage 104b or 104a, causes one or other edge of the cut-out 77d to overlie the exhaust port 72e, causing pressure in the chamber 107 to rise and shift the load-piston 77 axially rightwards, Fig. 4b, until the cut out again uncovers the exhaust port and stabilizes the piston in a position giving an increased regulated pressure. Further rotation of the selector valve 72 in the same direction results in additional follow up movement of the piston 77, so that the magnitude of the stabilized pressure corresponds to the rotational setting of the selector valve 72. Reverse gear, Fig. 15, comprises an input shaft 1 carrying a forward clutch CF driving a freely mounted wheel 6 meshing an output wheel 57, the latter also meshing a similar wheel on a parallel shaft reversely driven by an input wheel 7 and carrying a reverse clutch similar to CF. Friction clutches.-The forward and reverse clutches are identical, each comprising a disc pack engaged by applying liquid pressure to the right face of a piston 17, connected for rotation with the output member 13b by axial bolts 26. Pressure reaches the piston through a centrifugal valve 40 rotating with the output member and having a radial spool 42 urged inwards by supply pressure 21 supplied to an outer chamber 44, and outwards by spring and centrifugal force to cut off the pressure supply to the clutch above a predetermined speed, preventing increase in output speed and maintaining that speed constant for a given supply pressure. Fluid circuit. Fig. 17, not shown, includes an engine driven pump, suction screen, pressure filter, and a main regulator valve the discharge from which supplies lubricating and clutch cooling lines.